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# Ulnar notch cartilage

The ulnar notch cartilage lines the curved notch at the top of the [ulna](https://durgical.com/en/anatomy/ulna/) that wraps around the humerus; it makes the elbow hinge glide.

Official name: Cartilage of the trochlear notch

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## What it is

The smooth lining of the ulna's hook that wraps the humerus.

## What it does

Makes the elbow hinge glide.

## Key points

- The trochlear notch is formed by the olecranon above and the coronoid process below; its cartilage is often interrupted by a transverse bare strip at the waist, a normal finding
- The coronoid is the anterior buttress of the elbow: a coronoid fracture with a dislocation makes the joint unstable (terrible triad)
- The sublime tubercle on the medial side of the coronoid anchors the anterior bundle of the [UCL (elbow)](https://durgical.com/en/anatomy/ulnar-collateral-ligament-of-the-elbow/)

## Key facts

**Where**
Trochlear notch of the ulna (olecranon and coronoid process)

**Function**
Hinge surface on the humeral trochlea

## Relations

**In front**
Trochlea of the [humerus](https://durgical.com/en/anatomy/humerus/), which the notch grips like a wrench

**Behind**
Olecranon, with the [triceps tendon](https://durgical.com/en/anatomy/triceps-tendon/) insertion and the [olecranon bursa](https://durgical.com/en/anatomy/olecranon-bursa/) over it

**Below**
Coronoid process, with the [brachialis](https://durgical.com/en/anatomy/brachialis/) inserting on the ulnar tuberosity just below

**Medial**
Sublime tubercle with the UCL anterior bundle; the [ulnar nerve](https://durgical.com/en/anatomy/ulnar-nerve/) behind, in the cubital tunnel

**Lateral**
Radial notch for the radial head, ringed by the [annular ligament](https://durgical.com/en/anatomy/annular-ligament-of-the-radius/)

## How to find it

The olecranon, the upper lip of the notch, is the bony point at the back of the elbow and can be felt in any position; in flexion its upper surface leaves the fossa and becomes easy to feel. The cartilage itself is seen only at surgery, for example when an olecranon fracture is fixed.

## On imaging

A true lateral X-ray shows the arc of the notch, the coronoid tip and any olecranon displacement; CT defines coronoid fragment size and the anteromedial facet. On MRI the cartilage-free waist and the small notches at its edges are pseudodefects, not cartilage injuries.

## Clinical notes

- Olecranon fractures enter the joint surface; fixation (tension-band wiring or a plate) aims to restore a smooth notch
- Coronoid fractures are graded by fragment height (Regan–Morrey) and by site (O'Driscoll, which adds the anteromedial facet); a missed anteromedial facet fracture after a varus injury leads to instability and early arthritis
- In throwers, valgus extension overload drives the olecranon tip against the fossa, forming posteromedial osteophytes and wearing the cartilage at the back of the notch

## Development

The olecranon ossifies from a secondary centre late in childhood (the 'O' of CRITOE) that may look fragmented; a persistent or stress-widened olecranon physis is seen in young throwers.

## Test yourself

Think of the answer, then tap the question to see it.

## Which processes form the trochlear notch of the ulna?

The olecranon above and the coronoid process below.

## Why does a coronoid fracture with a dislocation make the elbow unstable?

The coronoid is the anterior buttress of the elbow (terrible triad).

## Which ligament attaches to the sublime tubercle of the coronoid?

The anterior bundle of the ulnar collateral ligament (UCL) of the elbow.

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Educational information, not medical advice. For any symptom, see a health professional.

## Its names

**Official Latin (TA2)**
cartilago articularis incisurae trochlearis ulnae TA2 382

**Official Spanish (DeCS)**
Cartílago articular de la escotadura troclear de la ulna

**English (TA2)**
Cartilage of the trochlear notch

## Related

- [Humerus](https://durgical.com/en/anatomy/humerus/)
- [Ulna](https://durgical.com/en/anatomy/ulna/)

Sources: Terminologia Anatomica (TA2); [Anatomy, Shoulder and Upper Limb, Elbow Joint](https://www.ncbi.nlm.nih.gov/books/NBK532948/); Anatomy of the Human Body (20th ed.): Surface Anatomy of the Upper Extremity (Lea & Febiger (Gray's Anatomy, 1918), 1918) · adapted, Public domain.

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Representative model, for educational purposes only.

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Source: https://durgical.com/en/anatomy/cartilage-of-the-trochlear-notch/
License: CC BY 4.0 (https://creativecommons.org/licenses/by/4.0/). Cite as: DurgiPedia (durgical.com), https://durgical.com/en/anatomy/cartilage-of-the-trochlear-notch/